Method of and apparatus for igniting fuel



May 25, 1948. w, H 2,441,965

METHOD OF AND APPARATUS FOR IGNITING FUEL' Filed March 29, 1946 2Sheets-Sheet 1 3 vweufoz Mil/am D. Hall 1 I f #4 M 3m f May 25, 1948. w.D. HALL 2,441,955

METHOD OF AND APIARATUS FOR IGNITING FUEL Filed March 29, 1946 2Sheets-Sheet 2 Wf/l/am D. Ha

Patented May 25. 1948 METHOD OF AND APPARATUS FOR IGNITING FUEL WilliamD. Hall, Elkins, W. Va.

Application March 29, 1946, Serial No. 658,195

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) 13 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates to methods of and apparatus for igniting andburning combustible fuel and has several objects and advantages. Theprimary object is to provide starting methods and means which increasesthe probability of ignition and reduces the likelihood of explosions.Another object is to provide a switch which quickly cuts off theelectrical igniter when combustion is established. Still other objectsand advantages of my invention will appear as this description proceeds.

When the fuel valve of an electrically ignited burner is opened, theinitial on rush of incombustible gases may so cool the igniter thatcombustion will not be effected. According to the invention now to hedescribed, the supply of fuel is purposely decreased to a low steadyquantity and then again increased to normal should it fail to ignite onthe first efiort at ignition. When is done, the cooling effect on theigniter ceases for a short while and as the fuel again increases it willordinarily ignite immediately. further advantage of this method is thatshould ignition he attempted when the main control valve is wide openand admitting a very large ly inside of the same prior to establishmentof combustion and is already heated to some degree before the fliameheats it. This will be discussed in detail later.

I have illustrated the various parts of my invention ratherdiagrammatically in the accompanying drawings since my invention relatesto methods and. systems generally rather than to specific details ofdesign of a particular system. Figure 1 illustrates fuel burningapparatus on which my invention may be performed manually. Figure 2illustrates schematically certain apparatus that will automaticallyoperate in accordance with the principles of my invention.

Figure 3 illustrates schematically another form of the invention.Figures 1 and 2 of this application and the description applicablethereto are identical with corresponding figures and description in mynow abandoned prior copending application S. N. 379,586, filedFebruary'l 1941, entitled the same as the present case and of which thepresent case is a continuation-in-part.

In Figure 1 a source of electricity which may be a. six volt storagebattery supplies power to wires it and ii. A. switch it is used to closethe circuit and initiate operation of the system. A bimetallic strip isis supported in the vicinity of the burner is by the bracket i i. Stripit carries a contact point it which normally engages conquantity of gas,the supply of such'gas is reduced so tact po that is, it engages p t itwhen during the ignition period. A still further advantage of this idearesides in the fact that in event ignition actually takes place theinstant prior to reduction in the quantit of fuel that the flame willnot be extinguished but will con- 35 tinue to burn.

it is common in the art to deenergize an electrical igniter with aseries connected thermo static switch. Such a switch does not instantlydeenergize the igniter when combustion is esen tablished. During theinterval when both the flame and the current are heating the igniter thelatter deteriorates. For this reason it is desirable to reduce the timelag of response of the thermostatic switch as much as possible in orderthat at the burner is cool. When the strip it is heated, it movescontact point it to the right and breaks contact between that point andits complementary contact point it. Contact point it is carried by astationary support ii and connects electrically to one end of theelectrical resistance igniter coil iii, which coil may be directly abovethe burner iii and in thepath of the oncoming fuel. While the ignitercoil is is shown in direct operative relation with the burner it I wishto state that such coil may be operatively associated with the burner inany of the well known indirect methods lrnown to the art. The gasissuing from the burner is is ignited by the coil iii, and such gas isfed to the burner through the fuel feed line it. A valve it is locatedin pipe ill but this valve is so constructed that it never completelycloses the fuel feed line. Even when the valve ii is fully seated, aspace 22 is open which permits some fuel to flow to the burner. A handle"it is controlled manually and it in turn controls the valve 2|. Thevalve 2! has enough friction in its operation that it will remain fullyopen or fully seated as the case may be when it rapidly because itreceives heat generated direct- 56 is left in either of these positions.A main control valve V may be used to completely shut down the system orto regulate the quantity of fuel fed thereto. v

To carry out the invention manually with the system of Figure 1, theswitch I2 is first closed. When this is done, the igniter coil I8 isimmediately energized and at the same time current flows through thebimetallic strip l3 heating it. Valves V and 2| are then completelyopened in turn to the desired degree If valve 2| is already completelyopen as would ordinarily be the case, only valve V need be opened. Whenthese valves are opened the supply of fuel may increase either graduallyor very rapidly depending on how fast they are opened. In either eventthe fuel may fail to ignite in which event the valve 2| should be fullyseated for a few seconds or so and then again fully opened. It is Veryprobable that should the fuel fail to ignite on the first effort due toimproper combustion conditions that it will ignite this second time. Ifthe fuel ignited at precisely the instant that the supply of fuel wasdecreased, the flame will not extinguish because valve 2| does not fullvclose. As has been stated there is an opening 22 below the valve 2|which permits some fuel to flow to the burner even when the valve isfully seated. Should the fuel fail to be ignited on the first or thesecond efforts. the valve handle 23 may be repeatedly operated up anddown until the fuel does ignite. It may be operated up and down eitherfast or slow depending on which manner is found most effective underparticular circumstances. During ll this time, the igniter coil l8remains continuously energized.

As soon as the fuel ignites, the strip i3 is heated and tends to openthe circuit at contacts 95 and IS. The prior art shows the sameelectrical circuit as I have shown in Figure 1, however, I contemplate abimetallic strip |3 of such size and resistivity that it will beappreciably heated by the flow of current therethrough to the igniter.Therefore, prior to the time the thermostatic switch I3, l5 breaks theigniter circuit the bimetallic strip I3 is heated by the current and dueto this heating breaks the circuit in less time than it otherwise would.This feature also permits the design to operate the switch I3 at ahigher temperature without increasing the response time above that nowused; hence the switch ill recloses the circuit quickly when the flamebecomes extinguished. By generating the ore-heating directly inside ofthe bimetallic strip it the effect of the heating is much more rapidthan it is when such pie-heating is accomplished by a series resistornear the strip. The degree to which bimetallic strip i3 is heated by theigniter current therethrough may be (a) sufiicient to actually break thecircuit at contacts i5, i6 even if the fuel completely fails to igniteat any time, or (b) it maybe insufficient to actually break the circuitat |5, |6 until additional heat is supplied by the flame. Preferably theheating is sufficient to bring the temperature of the strip I 3 almostup to the point at which it breaks the circuit at contacts i5, i6. Inthis case only a slight additional heating is necessary from the flame.to break the circuit and deenergize the igniter and of course this smallamount of heat will be supplied almost instantly after the fuel isignited. Of course, my claims are not to be limited to this high degreeof perfection but broadly cover the case where appreciable heat isgenerated inside strip l3.

The apparatus of Figure 2 will automatically accomplish the functionsperformed manually on the device of Figure 1. The various parts ofFigure 2 that bear'reference numbers common to Figure 1 are identical inconstruction and operation to similar parts of Figure 1.

In Figure 2, the valve 2| is operated by a cam follower 26. The followeror roller 26 is held in contact with the cam 29 by a spring 24. Thespring 24 is based upon pipe 20 and presses upward on arm 25 which armis rigidly fastened-to the valve 2|. The cam 29 is pivoted off center at28 and is driven by a motor 32. Contact points 3|] and 3| are separatedwhen the valve 2| is open and the contacts are together when the valve2| is fully seated. The parts are shown in the nor mal off position justprior to turnin it to the on position. To start the apparatus, theswitch |2 is thrown "on thus establishing an igniter circuit as follows:I0|2-|4-|3-|5|6|l |8--| The igniter |8 begins to become hot and strip I3is preheated due to the large igniter current flowing therethrough. Themotor 32 is also energized by the following path: ||l|2--|3|5|6-|'|-3332-| Resistor 33 is not large enough to prevent energizationof the motor by this circuit. If the fuel ignites immediately, theswitch 3 will break the igniter circuit as well as the motor circuitquickly, thereby leaving valve 2| fully open. If on the other hand thefuel should fail to ignite on the first effort, motor 32 will begin torotate the cam 25 slowly (as the motor is provided with suitablemechanism whereby it rotates the cam only very slowly). It requires saytwenty seconds or so to revolve the cam 29 a half revolution. When thevalve 2| approaches a seated position, contacts Bil and 3| engage eachother and thereby energize the motor as follows: |ll--|2--i|--|3fiexible lead 2'l 253il3|-- |9'32-l l. The motor is now energizedindependently of switch I5, l5 and will remain running until the valve2| is unseated. If by that time the fuel has ignited and has broken thecircuit at contacts I5, I6 the motor will stop in a valve-open positionupon the breaking of contacts 3i! and Eli. It is noted that the motorcan never stop in a valve-closed position. If the fuel fails to ignite,the cam 29 will continue to rotate thereby intermittently opening andseating the valve 211 and will therefore repeatedly decrease andincrease the ilow of gas striking the igniter coil it which of courseremains energized continuously. if switch it? opens while the valve isseated, the igniter it will. drop in temperature slightly belowincandescence due to resistor but will still be heated by the circuiti@-i2 li32f|253i|3 |'ti3l8-l l, until finally the valve 2| is fullyunseated at which time the igniter is completely deenergized due to theseparation of contacts 30 and 3|.

If the self-heating of switch I3 is designed to be sufficient toactually break the circuit by reason of the heavy igniter currenttherethrough even in event the flame never is established; then theigniter IE will be intermittently increased and decreased inenergization. Similarly the valve 2| will repeatedly open and reseatitself,

If the flame ignites, continues to burn for a while, then becomesextinguished, switch l5, l6 will close and cause the motor 32 to rotatecam 29 just as in the case of an initial ignition attempt. This willautomatically attempt to make several new attempts to again establishcombustion.

In Figure 3, a hot wire igniter I8 is connected to the center, tap 50 ofthe secondary of current transformer 5|. The ends 52 and 53 of thesecondary winding connect to the U-shaped bimetallic member 54 whichnormally maintains contact with contact point 55 but bends upward andaway from 55 when member 54 is heated. Contact 55 is in series withprimary winding hi and with source 51, 58. The motor 32 across theigniter operates the cam 29, cam follower 26, and valve 2! as is morecompletely shown in detail in Figure 2.

Eu Figure 3, when the starting switch is closed, current flows asfollows: 58--l9-5ll-52E3-- li l-llilfib-lil--tl. Flow of current throughprimary winding til causes a heavy current to ilow in the secondarywhich current circulates through the iJ-shaped member ti l. This heatingcauses member b l to be thoroughly heated and to greatly aid the heat ofcombustion in heating member 53 so as to break the circuit at Aftercontact at is broken the member so is heated by the flame only. Theprinciples of operation of Figure 3 can tently' increases and decreasesthe quantity of fuel fed through said feed line; a thermal switchcomprising a bimetallic strip and. contacts associated with, andseparated by, the strip when the strip is heated, and closed by thestrip when the strip is cooled; one of said contacts being electricallyconnected to one end of said strip; a wire ciao-- trically connectingthe other of said contacts to one of said terminals and also to one sideoi said hot-wire igniter; a wire adapted for connection to a source ofelectrical supply and connecting the remaining terminal as well as theremaining end of said hct wire igniter to one side of such source;another wire also adapted ior connection to a source of electricalsupply for connecting the remaining end of said bimetallic strip in sucha n manner that current from said source flows directly throughout thelength of said bimetallic strip before reaching said contacts; and meanssupporting said bimetallic strip to position the same responsive to theheat of combustion; said strip comprising materials of such size andresistivity that the flow of current directly therethrough to saidigniter will generate appreciable heat directly inside the strip andraise the ternperature of the strip close to the actual temperaturerequired by the strip in order to separate said contacts, whereby thestrip will operate to quickly separate the contacts in response tocombustion of fuel at said fuel burner.

2. in a fuel burning system, a burner, a hotwire ignite!" therefor, athermal switch comprising a thermal element, said thermal switch beingconnected directly in series with said igniter and such that the currentto the igniter flows directly through said thermal element, meanssupporting said thermal element responsive to combustion at said burner,and means operable to feed fuel to said burner; said thermal element andsaid igniter being composed of materials of such size and resistivitythat when energized the heating generated directly inside of saidthermal element by the igniter current fed therethrough will appreciablyraise the temperature of said element.

3. The system of claim 2 wherein the resistivity of said element is sohigh that the heat generated directly in the thermal element is so greatas to cause the switch to deenergize the igniter even in absence 0! heatof combustion.

4. The system or claim 2 in which the resistivity of the thermal elementis sufilciently low that the heating thereof due to the current flowingtherethrough will raise the temperature thereof above ambient to a lowervalue than is required to break the igniter circuit.

5. In a heating system, a space wherein fuel is burned, electricalenergized ignition means adapted to ignite the fuel when such means isenergized, a circuit ior energizing said ignition means and including acontrol means in series with the circuit, said control means including athermal element for operating the same to break the circuit when saidelement is heated and to close the circuit when said element is cooled,said control means comprising means for effecting flow of sufiiicentcurrent directly through said element when and only when the igniter isenergized to appreciably heat said element and provide at least tenpercent of the amount of heating that is required to be supplied to saidelement in order for the circuit to be broken by said element, wherebyto reduce the time lag of response thereoi to combustion, and supportingmeans positioning the thermal element responsive to the heat oi"combustion.

6. The method of utilizing an igniter oi the hot-member type toestablish combustion of fuel at a burner which includes heating theigniter, establishing a flow of fuel operatively near the ignlter. andmaintaining the igniter continuously energized while the supply of fuelis decreased to a low but substantial value at which it will sustaincombustion ii a flame was established on the first effort andsubsequently increased.

'7. The method of utilizing an igniter of the hot-member type toestablish combustio at a burner which includes varying the fuel flowrate across the igniter between a high rate and a low substantial ratewhile maintaining the igniter continuously energized.

8. "in a heating system, a burner, a hot-mern ber type igniter therefor,iuel feeding means, means for energizing the igniter and maintaining thesame continuously energized until combustion is established, and meansfor making more than one effort to effect combustion of the fuel at theburner, the last-named means comprising means for initially increasingthe flow or fuel so as to make a first effort and in event that effortfails to reduce such flow to a lower but appreciable quantity andsubsequently again increase such flow.

9. The method of utilizing an igniter oi the hot-member tyne toestablish combustion of fuel at a burner which includes heating theignlter, establishin a flow of fuel operatively near the igniter so asto cool the igniter if ignition is not effected, reducing the quantityof fuel fed near the igniter so that the igniter can rise in temperatureyet maintaining at all times suificient flow of fuel that if combustionis established that it will sustain itself, and subsequently againincreasing the flow of fuel.

10. In a heating system; a burner, a hot wire igniter that consumes alarge current when operating; said igniter being positioned near theburner so as to ignite fuel thereat; a thermal element composed of ahigh resistivity bimetallic strip; a stationary supporting currentconnection at one end of said. bimetallic strip; a contact point carriedby the other end of said bimetallic strip; a stationary currentconnection having a complementary contact point for the first-namedcontact point; wires energized by a low voltage large current supply forforcing the large current through said strip and igniter; said wiresforming a series circuit from the source to and through the igniter, toone of said stationary current connections, through said strip to theother stationary current connection, and back to the source; saidbimetallic strip being positioned in the region of heat from the burnerand operable upon establishment of combustion to rise in temperature andmove said contacts to a separated position to thereby break the ignitercircuit and deenergize the hot wire igniter in a predetermined timeinterval after combustion is established, and said bimetallic stripcomprising means whereby the large igniter current/flowing therethroughgenerates sufllcient heat directly inside of said bimetallic strip as tomaterially and substantially reduce the time required to break theignlter circuit below the time that would be required in event there wasno heat generated in the bimetallic strip by the igniter current; andswitching means operable to control the igniter circuit to close thesame, activate the igniter. and effectuate the said heating in saidbimetallic strip.

11. The heating system defined by claim in which the igniter is ahot-wire type igniter, and in which the thermal element consists of highresistivity material.

12. The device defined by claim 5 in which said control means comprisesa current transformer havingits primary in series with said circuit andits secondary connected across at least a portion of said element so asto pass a heavy current through the latter.

13. In a burner control system, a hot-wire igniter, a circuit energizingthe igniter, a transformer having a primary winding in series with saidcircuit, said transformer having a secondary winding, and thermostaticmeans comprising a bimetallic strip a portion of which is shunted acrosssaid secondary winding and thereby is heated by current from saidsecondary winding.

means supporting said thermostatic means near the flame so as to beheated thereby, and a switch in series with said circuit and operated bysaid thermostatic means to break said circuit when said thermostaticmeans is hot and to close said circuit when said thermostatic means is0001; said bimetallic strip and said igniter circuit being of suchimpedances that when energized the heating in said bimetallic strip bythe current passing therethrough will appreciably raise the temperatureof said bimetallic strip and thereby cause the igniter to be deenergizedmore promptly than it would have been deenergized had the bimetallicstrip been heated solely by heat from the flame.

WILLIAM D. HALL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re.19,235 Phelan July 10, 19341,575,170 Knopp Mar. 2, 1926 1,735,834 Mayo Nov. 12, 1929 2,149,853McCabe Mar. 7, 1939 2,268,229 Walle Dec. 30, 1941

